1. Technical Field of the Invention
The present invention relates to a method and an apparatus for diagnosing a fault in a semiconductor device, and more particularly to a non-contact method and a non-contact apparatus for diagnosing a fault in a semiconductor device by obtaining a two-dimensional electric field vector distribution in the semiconductor device. Photoexcitation is performed on the semiconductor device, and the radiant electromagnetic wave is then detected to obtain the electric field vector distribution.
2. Description of the Related Art
A technology of inspecting a semiconductor device without breaking the semiconductor device is used for detecting a defective PN-junction, a position of electrical wire breaking, short circuit or high resistance to perform quality analysis or defect analysis on the semiconductor device as described in Reference (Shigeo Horiuchi et al., “Electron Microscope Q & A”, p. 48, published by Agune Shohusha Co., Ltd. (Dec. 15, 1996)).
FIG. 1 shows a principle of a conventional method of inspecting a semiconductor device without breaking the semiconductor device. When a PN-junction 51 is irradiated with a laser beam 52, a pair of an electron 53 and a hole 54 is generated. The electron and the hole of this pair flow in opposite directions to generate a current, because of an electric field at a depletion layer of the PN-junction 51 and an electric field applied from an external power source 55. The current thus flowing is an optical beam induced current (simply referred to as OBIC current, hereinafter) resulting from an OBIC phenomenon. This OBIC current 56 is detected as a current or a current change measured by an ammeter 57 which is connected in series to the PN-junction 51.
FIG. 2 shows a conventional technique of detecting a defect by using an OBIC current in the same configuration as in FIG. 1. In FIG. 2, there is a defect 58 which promotes re-bonding of an electron and a hole at the PN-junction. When a portion having no defects is irradiated with a laser beam 52, an OBIC current flows in the same manner as in the case of FIG. 1. On the other hand, when the defect 58 which promotes the re-bonding is irradiated with a laser beam 59, even if a pair of an electron and a hole is generated, the pair is immediately re-bonded to disappear, causing no OBIC current to flow. Thus, it is possible to specify a defect position where the re-bonding is promoted.
The OBIC phenomenon at the PN-junction is used not only for detecting a defect at the PN-junction but also for detecting a position of wire breaking (as described in Japanese Laid-Open Patent Publication No. 10-135413, for example). A method of Japanese Laid-Open Patent Publication No. 10-135413 will be described with reference to FIG. 3 of a side view and FIG. 4 of a plan view.
PN-junctions 71, 72 and 73 are connected in series. A wire 63 is formed in parallel with each of the PN-junctions 71, 72 and 73. When a wire breaking defect 78 exists in the wire 63, an OBIC current flowing in the PN-junction 72 connected in parallel with the wire 63 having the wire breaking 78 differs in value from OBIC currents flowing in the other PN-junctions 71 and 73 so that the wire breaking 78 can be specified. Accordingly, similarly to the wire breaking, a short circuit defect and high resistance defect in the wire can be detected by taking advantage of the abnormality in an OBIC current.
To diagnose a fault in the semiconductor device by using the conventional techniques as described above, a bias voltage has to be applied to a chip (semiconductor device). Accordingly, electrical connection to an external voltage applying device has to be formed on the chip.
For this reason, there is a problem in that a fault in a semiconductor device cannot be detected during the manufacturing process for the semiconductor device. In other words, in the case of the conventional fault diagnosing, it is very difficult (practically impossible) to form electrical connection on the chip during the manufacturing process. Thus, it is impossible to detect a fault in the semiconductor device in a state where no bias voltage is applied to the semiconductor device during the manufacturing process.